Hub cap having an air valve for bearing cavity pressurization

ABSTRACT

A hub cap is provided for boat trailer wheel hubs that includes an air valve. The valve may take several different forms. A first embodiment hub cap employs a needle valve that is inserted through an aperture formed within the hub cap body. A second embodiment hub cap employs a Schrader-type valve. The valved hub cap allows the hub cavity to be temporarily pressurized when a boat trailer is partially submerged during the launch and recovery of a boat. Additional features may be incorporated in the hub cap, including a pressure release valve, which prevents damage to the hub seal, an O-ring groove in the hub cap body, which seals the cap to the hub and may also secure the hub cap to the wheel hub body. A separate spring retainer clip is also provided, which secures the hub cap to the hub body.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to hub caps for wheel hubs having taperedroller bearing races within a sealed cavity and, more particularly, tohub caps having an air valve through which the sealed cavity can bepressurized to prevent the inflow of water when the wheel hub issubmerged in water, as when hubs on a boat trailer are submerged in thewater during launching and recovery of the boat.

[0003] 2. Description of the Prior Art

[0004] Referring now to FIG. 1, a conventional boat trailer wheel hub100 typically has inner and outer tapered roller bearing assemblies 101Aand 101B, respectively. Each bearing assembly has an inner race 102 thatis mounted on the axle 103, an outer race 104 that is pressed into thehub body 105, and a plurality of tapered rollers 106 mounted in anannular roller retainer 107, which ride against both the inner and outerraces. As the races and tapered rollers are fabricated from hardenedsteel, they are extremely vulnerable to corrosion. Wheel hubs typicallyhave a cavity 108, which is spanned by the axle shaft between the innerand outer bearing assemblies, and open at both ends. The cavity isfilled with a high-temperature grease (not shown) in sufficient quantitythat the bearing races and rollers are continually bathed in liquifiedgrease as centrifugal force throws the grease against the cavity walls.The grease is retained within the cavity 108 by a hub cap 109, that ispressed into the nose 110 of the hub body 105 and seals the outeropening, and by a flexible, neoprene rubber seal 111, that seals theinner opening. The neoprene rubber seal 111 is molded into a metalretainer ring 112 that is pressed into the inner opening of the hub. Aflexible annular lip (not shown) on the neoprene rubber seal 111 ridesagainst a cylindrical sealing surface on the axle shaft.

[0005] Though entirely adequate to protect the bearing assemblies fromrain, the neoprene seal is unable to provide hermetic sealing when thehub assembly is submerged. Boat trailer wheel hubs are usually submergedin water during each launching and each recovery of the carried boat.Entry of water into the hub cavity occurs via the following mechanism.When the trailer is being towed, friction caused by a combination ofcontinuing movement of the bearing assemblies, contact of the tires withthe road and—if the trailer is so equipped—braking generates heat, whichcauses the air and grease inside the hub cavity to expand. When the hothub is submerged in water during launching of the boat, the hub coolsand the air and grease inside the hub cavity contract, thereby reducingthe pressure within the hub cavity below ambient atmospheric pressure.The neoprene rubber seal, which seals most effectively when the pressurewithin the hub cavity is greater than ambient atmospheric pressure,actually functions as a one-way valve when the pressure gradient isreversed. Water, sand, and other contaminants flow into the hub cavityuntil the pressure within the hub is equal to the ambient atmosphericpressure. Once water has found its way into the hub cavity, destructionof the bearing assemblies and possibly the axle shaft via corrosion isinevitable.

[0006] The problem of bearing corrosion in boat trailer hubs has spawneda multitude of inventions aimed preventing water from entering into thehub cavitys of trailer wheels. Some of the preventative measures coveredby these inventions are costly to implement, others are complex, othersare costly, and some are ineffective. The following patents areexemplary of the prior art.

[0007] In U.S. Pat. No. 3,785,706, issued to Vangalis on Jan. 15, 1974,there is disclosed a pressurized hub cap for a vehicle wheel. TheVangalis patent describes a cup-shaped cap having a flange which seatson the wheel hub. A helical spring urges a piston in the direction ofthe axle of the trailer to hold grease on the outside of the axle andassociated nut. A vent hole is provided on the outside of the piston,and a second hole is provided to allow the escape of grease in the eventthat excessive expansion of the grease occurs. A similar construction isdescribed in U.S. Pat. No. 4,106,816, issued to August on Aug. 15, 1978.In U.S. Pat. No. 3,955,852, issued to De Puydt et al. on May 11, 1976,there is also described a trailer hubcap device utilizing aspring-biased piston to pressurize grease against the outside of theaxle and nut. The De Puydt et al. patent further describes a manualactuator to permit the pressure to be relieved while the trailer isbeing moved along a roadway.

[0008] A related hubcap construction is described in U.S. Pat. No.3,649,080, issued to Molinare on Mar. 14, 1972. This patent describes ahubcab construction which includes a grease fitting to permitintroduction of grease into the cap and also a pressure relief valve toprovide for expansion of the grease. In U.S. Pat. No. 3,393,015, issuedto Kaufman of Jul. 16, 1968, there is described a hubcap which includesan O-ring normally positioned over a vent hole to prevent the entranceof water within the cap, but which will expand to uncover the hole forpermitting air and grease to be vented from the hubcap when heated. Aprotective hubcap closure is described in U.S. Pat. No. 3,149,883,issued to Reilly on Sep. 22, 1964. The Reilly patent describes a hubcapwhich is flexible to become contracted or compressed when the trailer isimmersed in cold water.

[0009] A different approach to the waterproofing for a hubcap isdescribed in the Eberle patent, U.S. Pat. No. 3,226,162, issued on Dec.28, 1965. The Eberle patent describes the use of a tube connecting fromthe pressurized tire to the hubcap, for permitting air to be vented intothe hubcap as a method for pressurizing the cap to prevent entrance ofwater.

[0010] Several types of pressure relief hub caps have been produced inthe past. One type is shown in U.S. Pat. No. 3,785,706 to Van Galis. Inthis device, a cup shaped seal is mounted within a cup shaped hub cap,with a spring acting on the seal to compress the grease within the hub.A first opening in the cap adjacent the outer end provides for pressurerelief in the spring area between the seal and the outer end of the hubcap. A second opening in the hub cap inboard from the first openingprovides for escape of grease when the pressure within the hub issufficient to compress the spring.

[0011] Another type of hub cap is shown in U.S. Pat. No. 3,077,948 toLaw. This structure utilizes a cup shaped seal sliding in a sleeve witha spring urging the seal inward to compress the grease. The sealingaction occurs between the cup shaped seal and an O-ring in the innersurface of the sleeve. A grease fitting is carried in the sliding sealfor introducing grease into the hub.

[0012] The hub cap of the U.S. Pat. No. 3,785,706 patent suffers fromthe disadvantage that grease can be added to the hub only by removingthe hub cap. This problem is solved by the hub cap of the U.S. Pat. No.3,077,948 patent. However there are still some disadvantages with thisstructure. When the hub is being filled with grease by a grease gun, themanual force utilized in holding the grease gun in place also acts tohold the sliding seal in fixed position so that excess pressure can bebuilt up within the hub and the inner bearing seal can be damagedwithout the operator knowing of this fact. That is, the automaticpressure release operation is nullified by the force applied with thegrease gun. Also, the cup shaped seal which slides within the outersleeve or housing and engages the O-ring for making a seal provides onlylimited area for escape of grease.

[0013] One of the more popular devices for affording protection to thebearings of trailer wheels is covered by U.S. Pat. No. 4,106,816 toAugust. Known as the “Bearing Buddy”, the device is a specially designedhub cap having a sliding piston with a centrally-positioned greasefitting. The piston is biased with a coil spring and is designed tomaintain the bearing bathed in grease. One of the problems with thisdevice is that it is impossible to remove all of the air from the cavityby injecting grease from the outer end of the hub, as the inward hubseal will prevent the escape of pressurized air that builds up as greaseis injected into the bearing cavity. Because the trapped air and greasehave different rates of expansion, it is difficult for the device towork as intended. Another problem is that the spring constantlypressurizes the bearing cavity of the wheel hub. This added pressureforces the wiping portion of the inner neoprene seal more firmly againstthe outer surface of the axle shaft. The added pressure increases thewear rate of the seal.

[0014] Accordingly, it is an object of the present invention to providea new and improved hub cap that is both simple to use and inexpensive tomanufacture, for sealing against the entrance of moisture into thebearing cavity. It is the intent of the present invention to preventwater and other contaminants from entering a boat trailer wheel hub byproviding temporary pressurization of the wheel hub cavity at times whenthe boat trailer must be partially submerged during the launch andrecovery of a boat.

SUMMARY OF THE INVENTION

[0015] The present invention provides a hub cap for wheel hubs thatincludes an air valve. The valve may take several different forms. Afirst embodiment hub cap employs a needle valve that is inserted throughan aperture formed within the hub cap body. An advantage of such a valveis that it is low profile and unlikely to be damaged by towing thetrailer too close to stationary objects. A second embodiment hub capemploys a Schrader-type valve that is inserted through an apertureformed within the hub cap body. Each of these valves allows the hubcavity to be temporarily pressurized when a boat trailer is partiallysubmerged during the launch and recovery of a boat. It is intended thatthe hub cavity pre pressurized only during periods when the wheel hub issubmerged, as traveling extended distances with the additional pressurewill increase the temperature and wear of the neoprene seal thatprevents the escape of grease between the hub and axle at the inneropening of the bearing cavity. Sufficient air pressure is added to thewheel bearing cavity so that it remains above the sum of ambientatmospheric pressure plus the added pressure caused by the depth ofsubmersion, even when a hot hub assembly is submerged in water and theinner pressure is reduced as the hub cools to the temperature of thewater.

[0016] One of the problems associated with pressurizing the hub cavityis the possibility that the hub cap will be blown off the hub. When hubcaps are new, a near perfect interference fit exists between the nose ofthe wheel hub and the cap. Given the presence of grease, an air tightseal is provided. However, with age and repeated removals of the hubcap, the sealability decreases. Therefore, another aspect of the presentinvention is the provision of a retainer clip that can be installed overthe hub cap and clip into grooves which are cut in the nose of the wheelhub. A boat trailer owner, exercising a reasonable amount of care, cancut the grooves in the wheel hub with a cut-off wheel on a hand grindertool.

[0017] An alternative retaining device for the pressurized hub caps is aramped annular groove stamped in the hub cap in the portion that isinserted in the nose of the wheel hub. An O-ring is installed within theramped groove. Given the direction and shape of the ramp, the hub capcan be easily inserted into the wheel hub. However, removal of the capcauses the O-ring to slide up the ramp, forcing it against both thegroove and the inner surface of the nose of the wheel hub and preventingthe hub cap from being easily removed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The invention may take physical form in certain parts andarrangement of parts, a preferred embodiment of which will be describedin detail in this specification and illustrated in the accompanyingdrawings which form a part hereof. In the drawings:

[0019]FIG. 1 is a cut-away perspective view of a trailer hub and axleassembly, complete with two sets of installed bearing assemblies and aconventional hub cap shown as ready for attachment thereto;

[0020]FIG. 2 is an isometric view of a first embodiment valved hub cap,which has a needle valve installed therein for injecting air into thebearing and axle cavity of a wheel hub;

[0021]FIG. 3 is a cross-sectional view of the first embodiment valvedhub cap, taken through the needle valve and axis of rotation of the hubcap;

[0022]FIG. 4 is an isometric view of a second embodiment valved hub cap,which has a Schrader-type valve stem installed therein;

[0023]FIG. 5 is a cross-sectional view of the second embodiment valvedhub cap, taken through the central axis of the valve and the axis ofrotation of the hub cap;

[0024]FIG. 6 is a top planar view of a hub cap retainer clip;

[0025]FIG. 7 is a bottom planar view of the hub cap retainer clip ofFIG. 6;

[0026]FIG. 8 is a side elevational view of the hub cap retainer clip ofFIGS. 6 and 7;

[0027]FIG. 9 is a modified second embodiment valved hub cap which alsoincorporates both a pressure release valve and an O-ring groove in whichan O-ring has been installed;

[0028]FIG. 10 is an enlarged view of region F10 of FIG. 9, showing thedetail of a retaining groove having a ramped cross section.

[0029]FIG. 11 is an enlarged view showing an O-ring installed in anO-ring groove of conventional cross section;

[0030]FIG. 12 is a side elevational view of the external portion of awheel hub, modified in accordance with the present invention and havinga first embodiment valved hub cap installed therein, that is secured tothe wheel hub with the retainer clip of FIGS. 6, 7 and 8;

[0031]FIG. 13 is an alternative embodiment of a hub cap retainer deviceshown ready for attachment to a hub having a hub cap installed therein;and

[0032]FIG. 14 is a wheel hub that has been modified to include aSchrader-type valve in the hub body.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0033] The various embodiments of the invention will now be describedwith reference to the accompanying drawing figures. It should beunderstood that the drawings are merely illustrative of the invention,are not intended to limit the scope thereof, and are not necessarilydrawn to scale.

[0034] Referring now to FIG. 2, a first embodiment hub cap 200 employs aneedle valve 201 that is inserted through an aperture 202 formed withinthe hub cap body 203. An annular flange 204 limits the amount that thehub cap 200 may be inserted into the nose of the wheel hub. An inflatingneedle 205, identical to those used to inflate balls and other sportsequipment, is shown positioned in an axial relationship with the hubcap. The cap is designed to replace a standard hub cap of the type shownin FIG. 1. An advantage of the needle valve 201 is that it has a lowprofile that minimizes the potential for damage caused by by towing thetrailer too close to stationary objects.

[0035] Referring now to the cross-sectional view of FIG. 3, theconstruction of the needle valve 201 is shown in greater detail. Theneedle valve 201, which is radially symmetrical about a needle insertionaxis 301, is designed so that as air pressure is increased on the insideof the hub cap with respect to ambient air pressure on the outside ofthe hub cap, the valve seals more tightly.

[0036] Referring now to FIG. 4, a second embodiment hub cap 400 employsa Schrader-type valve 401 that is inserted through an aperture 402formed within the hub cap body 403. An annular flange 204 limits theamount that the hub cap 400 may be inserted into the nose of the wheelhub. The use of a Schrader-type valve has several advantages. Firstly,the valves are extremely durable and extremely reliable. Secondly, anumber of screw-on pressure-indicating caps are available for thesevalves. By using a pressure indicating cap in combination with thepresent invention, the air pressure within the bearing cavity can bereadily and visibly monitored without a separate pressure gauge. Adisadvantage to the use of a Schrader valve is that it extends outwardlyfrom the hub cap, making it vulnerable to damage if the associatedtrailer is towed too close to stationary objects.

[0037] Referring now to the cross-sectional view os FIG. 5, it will benoted that a Schrader-type valve 401 has a replaceable valve core 501that screws into the valve stem 502.

[0038] Referring now to FIGS. 6 through 8, a spring retainer clip 600has a central aperture 601 that is sized to fit over the outer end of ahub cap 200 or 400. The annular flange 204 is larger in diameter thanthe central aperture 601, thereby acting as a stop for the circularportion 602 of the retaining clip 600. The retainer clip 600 hasmultiple hooked projections 603 which extend from the circular portion602, and are oriented toward the wheel hub 101. The nose 110 of thewheel hub 100 can be easily modified to receive each of the hookedprojections 603. FIG. 12 shows the modifications required. Spring steelis deemed to be the preferred material from which the retainer clip 600is fabricated.

[0039] Referring now to FIG. 9, a modified second embodiment valved hubcap 400A includes a pressure release valve 901, that is installed in thehub cap body 403. The pressure release valve limits maximum pressurewhen the hub cavity is pressurized so that the inner seal will not bedamaged by excessive pressure. The maximum allowable pressure, that isdetermined by the spring constant of a spring incorporated into thepressure release valve 901, is deemed to be about 30 pounds/square inch.The modified second embodiment valved hub cap 400A also includes acircumferential O-ring groove, in which is seated a neoprene rubberO-ring. The O-ring helps to seal the outer opening of the hub cavity108. The O-ring groove may be designed so that the O-ring also helpsprevent the unwanted removal of the hub cap 400A from the hub 100. Theportion of FIG. 9 identified as F10 is enlarged in FIG. 10.

[0040] Referring now to FIG. 10, enlargement of region F10 of FIG. 9shows the ramped shape of O-ring groove 1001. When the hub cap body203/403 in inserted into the nose 110 of the hub 100, the O-ring 1002 ispushed against the right side of the groove 1001. However, when the hubcap body 203/403 is retracted from the nose 110 of the hub 100, theO-ring 1002 rolls up the ramp, wedging itself between the ramped groove1001 and the inner surface of the nose 110 of the hub body 105. Thegreater the removal force, the tighter the O-ring is wedged between thetwo surfaces. It is necessary to destroy the O-ring in order to removethe hub cap.

[0041] Referring now to FIG. 11, an enlarged view of a region analogousto region F10 of FIG. 9 shows an O-ring 1002 installed in an O-ringgroove 1101 of conventional shape. The hub cap body 203/403 may beinstalled and removed from the nose 110 of the hub body 105 with aboutequal force.

[0042] Referring now to FIG. 12, a retainer clip 600 is shown installedover a first embodiment valved hub cap 400 and clipped to the nose 110of a hub body 105. Equiangularly-spaced grooves 1201 have been cut inthe nose to receive each of the hooked projections 603. Such grooves maybe easily cut using a cut-off wheel mounted on a hand grinder, such asthose manufactured and sold by Dremel, Inc. It will be noted that theannular portion 602 of the clip 600 rides the annular flange 204 of thehub cap. It should also be obvious that either a first or secondembodiment valved hub cap (200 or 400, respectively) may be so attachedto the nose 110 of the hub body 105.

[0043] Referring now to FIG. 13, a second embodiment hub cap retainingdevice 1300 includes an annular member 1301, to which are attached aplurality of spring clips 1302. The device functions in an identicalmanner to the spring clip 600 of FIGS. 6-8.

[0044] Referring now to FIG. 14, a modified conventional hub 100Aincludes a Schrader valve 1401 that is threadably inserted in a drilledand tapped hole in the hub body 105. Rather than pressurizing the hubcavity 108 through the hub cap, it can be pressurized through theSchrader valve 1401. The Schrader valve 1401 may be removed with awrench so that the wheel may be removed from the hub.

[0045] The preferred embodiments have been described, hereinabove. Itwill be apparent to those skilled in the art that the above methods mayincorporate changes and modifications without departing from the generalscope of this invention. It is intended to include all suchmodifications and alterations in so far as they come within the scope ofthe appended claims or the equivalents thereof.

What is claimed is:
 1. A hub cap for use on boat trailer wheel hubshaving a sealed chamber containing a pair of roller bearing assemblies,said hub cap comprising: a hub cap body that is generallycylindrically-shaped and closed at an outer end thereof, said hub capbody having an aperture therein; an air valve secured within theaperture, said air valve being readily accessible when the hub cap isinstalled in a wheel hub, so that air may be pumped into the sealedchamber.
 2. The hub cap of claim 1, wherein said aperture is located inthe closed outer end of the hub cap body.
 3. The hub cap of claim 1,wherein said air valve is a needle valve.
 4. The hub cap of claim 1,wherein said air valve is of the Schrader type.
 5. The hub cap of claim1, which further comprises a pressure release valve to limit the maximumamount of air pressure that may be pumped into the sealed chamber. 6.The hub cap of claim 1, which further comprises: a circumferentialO-ring groove in the hub cap body; and an O-ring installed in the O-ringgroove, said O-ring being compressed between the hub cap body and thewheel hub when the hub cap is installed in the wheel hub.
 7. The hub capof claim 6, wherein said O-ring groove is upwardly ramped in a directionaway from the closed outer end.
 8. The hub cap of claim 1, which furthercomprises: an annular flange that limits entry of the hub cap into thewheel hub; and a retaining device that biases against the annular flangeand attaches to the wheel hub with spring clips.
 9. A method forpressurizing the sealed chamber of a boat trailer wheel hub, saidchamber containing a pair of roller bearing assemblies, the methodcomprising the steps of: providing a hub cap that incorporates an airvalve therein; sealing an outer end of the wheel hub with said hub cap;pumping air into the sealed chamber.
 10. The method of claim 9, whichfurther comprises the step of providing an O-ring seal between the hubcap and the wheel hub.
 11. The method of claim 9, which furthercomprises the steps of: providing a circumferential O-ring groove oframped cross section in the hub cap; and providing an O-ring of suitablesize for installation in said O-ring groove.
 12. The method of claim 9,which further comprises the steps of: providing an annular flange thatlimits entry of the hub cap into the wheel hub; and providing aretaining device that biases against the annular flange and attaches tothe wheel hub with spring clips.
 13. The method of claim 9, wherein thevalve is of the Schrader type.
 14. The method of claim 9, wherein thevalve is a needle valve.
 15. A method for pressurizing the sealedchamber of a boat trailer wheel hub, said chamber containing a pair ofroller bearing assemblies, the method comprising the steps of: drillinga valve installation hole in the wheel hub body; threading the valveinstallation hole; providing an air valve having an externally treadedstem that threadably engages the threaded valve installation hole; andpumping air into the sealed chamber.
 16. The method of claim 15, whereinsaid valve is of the Schrader type.